首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   490157篇
  免费   4939篇
  国内免费   2079篇
化学   241916篇
晶体学   6826篇
力学   24108篇
综合类   61篇
数学   69256篇
物理学   155008篇
  2020年   3276篇
  2019年   3608篇
  2018年   11897篇
  2017年   12579篇
  2016年   10238篇
  2015年   5140篇
  2014年   6974篇
  2013年   17625篇
  2012年   17351篇
  2011年   27143篇
  2010年   17844篇
  2009年   17772篇
  2008年   24341篇
  2007年   27280篇
  2006年   15221篇
  2005年   18931篇
  2004年   15127篇
  2003年   13811篇
  2002年   12070篇
  2001年   12405篇
  2000年   9627篇
  1999年   7144篇
  1998年   6068篇
  1997年   5939篇
  1996年   5929篇
  1995年   5242篇
  1994年   5248篇
  1993年   5191篇
  1992年   5520篇
  1991年   5692篇
  1990年   5336篇
  1989年   5213篇
  1988年   5195篇
  1987年   5047篇
  1986年   4751篇
  1985年   6465篇
  1984年   6677篇
  1983年   5535篇
  1982年   5862篇
  1981年   5654篇
  1980年   5293篇
  1979年   5657篇
  1978年   5930篇
  1977年   5816篇
  1976年   5915篇
  1975年   5398篇
  1974年   5559篇
  1973年   5664篇
  1972年   4161篇
  1971年   3384篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
101.
Bruzy  N.  Coret  M.  Huneau  B.  Kermouche  G.  Mondon  M.  Bertrand  E.  Stainier  L. 《Experimental Mechanics》2019,59(8):1145-1157

The allotropic phase change from ferrite to austenite represents a moment of massive interplay between the microstructural and mechanical states of iron. The difference of compacity between the two phases induces a microplastic accommodation in the material at grain scale. However, mechanical heterogeneities resulting from the transformation process remain challenging to characterise due to the high temperature conditions it is associated with. We developed experimental equipment for in situ observation of α ? γ and γ ? α transformations. Images of the surface of an iron sample taken by an optical camera were used as input for a Digital Image Correlation (DIC) routine. Special care was taken to maximize image resolution to capture sub-grain phenomena. Observations show that, at the mesoscopic scale, shear strain fields exhibit strong localisations that are evidence of transformations that are occurring.

  相似文献   
102.
Popel  S. I.  Golub’  A. P. 《JETP Letters》2022,115(10):596-601
JETP Letters - One of the main features of the dusty plasma compared to the conventional plasma (without charged dust particles is anomalous dissipation that is caused by the charging of dust...  相似文献   
103.
Russian Journal of General Chemistry - Highly dispersed CaO has been synthesized by heating an aqueous solution of calcium nitrate and D-glucose up to 800°C. Calcium oxide is formed with an...  相似文献   
104.
Tetrahydrotetrazoles are five‐membered‐ring heterocycles containing four contiguous saturated nitrogen atoms. Very few examples of such compounds have been reported in the literature. Our previous attempt at the synthesis of a member of this class of compound suggested that the N—N bonds may be more labile than expected. This finding raised the question as to whether the structures of any of the previously reported tetrahydrotetrazoles had been properly assigned. We have reproduced the synthesis of a reported tetrahydrotetrazole, namely 1,2‐di‐tert‐butyl 3‐phenyl‐1H,2H,3H,10bH‐[1,2,3,4]tetrazolo[5,1‐a]isoquinoline‐1,2‐dicarboxylate, C25H30N4O4, and have now confidently confirmed its structure via X‐ray crystallography. However, while sufficiently stable in the crystal phase, we discovered that it remains very labile in solution (having a half‐life of only 15 min at 20 °C in CDCl3). A tentative reaction pathway for its dissociation based on 1H NMR spectral evidence is provided.  相似文献   
105.
106.
Crystallography Reports - The formation of Zn-based nanotubes by electrochemical synthesis in pores of template polymer matrices is considered. It is established that the number of defects in the...  相似文献   
107.
Journal of Thermal Analysis and Calorimetry - The paper focuses on the analytical analysis of the propagation of a normal shock wave in an adiabatic gas flow with nanoparticles. A modified...  相似文献   
108.
Crystallography Reports - The specific features of the formation of concentration inhomogeneities in crystals grown by the Czochralski method (GaSb:Te, Ge:Ga) and by the Bridgman method...  相似文献   
109.
Journal of Russian Laser Research - We discuss the use of high-pressure high-temperature (HPHT) diamonds for the determination of trace amounts of various Raman active substances. The amount of the...  相似文献   
110.
Journal of Solid State Electrochemistry - In this study, galvanostatic electrolysis, through the use of the platinum supported on Ti (Ti/Pt) and Ti/TiO2-nanotubes/PbO2 anodes, was conducted in an...  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号